This invention relates to a magnetoresistive device and in particular to a magnetoresistive device using a magnetoresistive thin film.
In a conventional magnetoresistive film made of a permalloy alloy, its output voltage varies in the form of a cosine function with respect to a magnetic field applied, as disclosed in Ching Tsang: "Magnetics of small magnetoresistive sensor", J. Appl. Phys. 55(6), 1984, p. 2226. That is, the electric resistance .rho. of the permalloy film exhibiting such a change as indicated by a curve 1 in FIG. 1 can be represented by a relation of .rho.=.rho..sub.0 +.DELTA..rho..multidot.cos.sup.2 .theta., where .rho..sub.0 indicates the resistance of the permalloy film when there is no magnetic field, .DELTA..rho. a variation in magnetoresistance, and .theta. an angle defined by the direction of a current flowing through the device and the direction of magnetization of the permalloy film. Thus, there is no substantially linear part in the magnetic field-output voltage characteristics curve. This remarkably influences the characteristics of a magnetic device in which a permalloy alloy film is used. For example, in the case where a conventional permalloy alloy film having such a non-linear magnetic field-current characteristic is used in a magnetoresistive type magnetic head, there takes place a problem that the range of the intensity of a bias magnetic field, which can be used, is restricted.